Vitamin D has been associated with a decreased risk of multiple sclerosis (MS). In this study, serum 1, 25-dihydroxyvitamin D (1, 25-(OH)2 vitD) and 25-hydroxyvitamin D (25-OH vitD), regulatory T cell percentages and naïve and memory T helper cell subsets were measured in 26 patients with multiple sclerosis, 21 who were not on treatment with disease modifying therapy. These studies showed an inverse correlation between 25-OH vitD levels and Treg cell percentages and a direct correlation between Treg cell percentages and 1, 25-(OH)2 vitD:25-OH vitD ratios. In addition, 25-OH vitD levels correlated directly and 1, 25-(OH)2 vitD:25-OH vitD ratios correlated inversely with CXCR3+ naïve T helper cell percentages and CXCR3+naïve:CXCR3+ memory T helper cell ratios. All together, these data demonstrate that vitamin D measurements can reflect measures of immune status among patients with MS.